In order to reduce friction and to be able to withstand heavy loading, drawer slides for such applications as file cabinets employ bearings to reduce wear. Two types of slides are commonly used in file cabinets.
One type of slide which employs two or three channels can be taken apart in order that the outer slide can be attached to the cabinet wall and the inner slide attached to the side of the drawer or vice versa. In such applications, a bearing cage retainer is used in conjunction with metal ball bearings. The former retains the balls between the retainer and the inner side of the flange. Clearly the apertures in the bearing retainer have a smaller circumference than that of the balls.
In other applications where it is not necessary to take apart the drawer slide after assembly for later installation in the cabinet a second type of drawer slide is used. In this second type of drawer slide, different retainers can be used. All of these retainers have in common apertures in the retainer which are larger than the diameter of the balls. The balls are prevented from laterally displacing by the two adjacent flanges of the channels. Since these channels are not disassembled during installation on the drawer and cabinet the second type of retainer can be used.
One model of this second type of retainer is manufactured from plastic in the form of a channel having upturned side flanges much the same as the metal channel slides used to form the slide itself. Apertures are made along both flanges and balls are inserted during assembly.
Another model of this second type of retainer in use, employs a longitudinal plastic bar which fits between the flanges of the outer and intermediate or intermediate and inner channels. It has two or more apertures in which metal balls are inserted (often by hand) during assembly.
It is the second type of slides, that is to say those which are not disassembled for installation, to which the present invention pertains.
All of the aforementioned drawer slides have certain problems. Firstly the retainers are expensive. Secondly they take up additional valuable space in the drawer cabinet application. In addition the metal retainers are cumbersome to fabricate, and the slide assembly process is time consuming. Retainers must be placed in the channels by hand and then balls loaded pneumatically through ball bearing feed lines. Human error often occurs or the machine malfunctions resulting in a large number of balls escaping around the work area and causing a safety hazard. Another problem exists because of the shape of the metal balls. Because of the spherical shape all of the mating raceways of the flanges of the channels must be circular in configuration. When a three part slide is used and two sets of friction reducing retainers are used significant waste in materials and space is encountered.